This invention relates to braid production, and more particularly to a braid product formed on a mandrel, the mandrel approximating the shape of a wheel with a varying radius of curvature.
It is known in the art that a variety of braided products may be formed over mandrels having the desired shape of the braided product. One common type of mandrel onto which a braid can be formed is straight in shape, with a fixed central longitudinal axis oriented to be coaxial with the braid axis. As a result, the braid is applied symmetrically around the mandrel. Another type of mandrel is circular in shape (like a wheel), with the braiding surface of the wheel being tangentially aligned with the longitudinal axis of the braiding apparatus. The wheel is further oriented so that the cross-section of the mandrel is centered in the braiding apparatus. As a result, the center point of the cross-section of the mandrel along its circumferential length remains coaxial with the braiding point as the wheel is rotated around its center, supporting a symmetric application of the braid.
However, where the shape of a mandrel approximates a circle or wheel with an irregularly varying radius of curvature, symmetrical application of braid around the mandrel and along its circumferential length cannot be accomplished by simply rotating the mandrel about an approximate center. Therefore, there is a need for a braiding machine and process to apply braid symmetrically to mandrel with a shape which approximates a circle or wheel but has an irregularly varying radius of curvature.
Disclosed are machine and method for applying braid by means of a braiding machine to a mandrel, where the mandrel has an irregularly varying radius of curvature along its length. The braiding machine includes a braiding apparatus for depositing a tubular braid over the mandrel by drawing yarns toward a braiding point where the tubular braid is initially formed on the mandrel. The braiding point lies along a central axis of the braiding apparatus that may be oriented, for example, in a y-direction.
The braiding machine further includes at least one mandrel placement assembly for positioning the mandrel in an x-direction within a plane that is orthogonal to the central axis at the braiding point, and for advancing the mandrel along its length. As the mandrel is advanced, the mandrel placement assembly repositions the mandrel relative to the x-direction so that a center point of a cross-section of the mandrel that lies in a plan that is orthogonal to the central axis is made to be coincident with the braiding point.
Each mandrel placement assembly includes opposing drive/positioning wheels for frictionally contacting opposing outer surfaces of the mandrel in reference to a center point of the radius of curvature, respectively. The opposing drive/positioning wheels are operative to rotate in frictional contact at least one of the outer surfaces of the mandrel, thereby advancing the mandrel along its length.
The opposing drive/positioning wheels are carried by a carriage that is pivotable about an axis that is transversely positioned with respect to the central axis of the braiding apparatus, and is fixed in relation to the braiding point. The drive/positioning wheel assemblies further include opposing side wheels orthogonally positioned in relation to the opposing drive/positioning wheels, for maintaining the position of the mandrel with respect to a z-direction of the braiding machine.
The opposing drive/positioning wheels are rotated by means of a drive mechanism coupled to one or more motors, and the drive/positioning wheels, carriage and side wheels are manipulated by means of linkage mechanisms couple to linear actuators. The motors and linear actuators may be controlled, for example, by a computer numerical control (CNC) controller which is operable to determine a current position of the mandrel at the braiding point in the x-direction as a function of the radiuses of curvature along the length of the mandrel.